This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. For bone regeneration, a key issue is to build a degradable scaffold that has appropriate mechanical strength during bone regeneration and suitable degradation rate (i.e., degradation of scaffold matching bone formation in the scaffold). It also must have a large size (a length of 10-15cm) and are easy to be processed. At present, polymeric scaffolds, such as poly lactic acid, degrade simultaneously in the whole scaffold, and lead to the scaffold collapse before the accomplishment of bone regeneration. On the other hand, commonly used metallic biomaterials including stainless steels and titanium alloys can release toxic metallic ions and/or particles through corrosion or wear processes, which cause inflammatory cascades and tissue loss. Further, these metallic biomaterials have much higher elastic moduli than natural human bones, and consequently, they can cause reduced stimulation of new bone growth. The proposed project will concern Mg-based alloy for bone regeneration. Pure magnesium has low density and is exceptionally lightweight. It has high fracture toughness, and it is essential to human metabolism and is naturally found in bone tissue. But, pure magnesium corrodes too fast in the physiological pH (7.47.6) and high chloride environment of the physiological system, and is not appropriate for bone regeneration. Therefore, there is urgent need to develop Mg-based alloys that can degrade at a rate comparable to the rate of bone formation in the scaffold. Further, the as-sought Mg alloys must have elastic moduli that are as close as possible to that of human bones and sufficient strength. Lastly, the toxic elements in the Mg alloys must be strictly controlled. These will be served as the screening tools for alloy development. The VASP package that solves for the electronic band structure using electronic density functional theory will be used in this project to calculate electronic structure and accordingly the elastic and thermodynamic properties of various Mg-based alloys. A number of potential alloying elements such as Al, Li, Zn, Y, La, Ce, Ag etc. will be considered. The phase stability of Mg-based binary, ternary and higher-order systems including solubility prediction will all be calculated at the low temperature limit. The elastic properties (e.g. Youngs modulus, yield strength, Poisson ratio) of both solid solution of hcp (hcp=hexagonal close packed) Mg alloys and the very Mg-rich compounds of multi-component system will be one focus of this project. The other focus will concern the possible reactions when the alloy in interest is in the electrolytic physiological environment. To begin with, only H2O and Cl- ions will be considered at the low temperatures limit.